Add CMake build system; remove obsolete build configurations

- Add root CMakeLists.txt that builds the FirebirdODBC.dll driver
- Add IscDbc/CMakeLists.txt for the IscDbc static library
- Add cmake/ helper modules:
  - FetchFirebirdHeaders.cmake: downloads Firebird 5.0.2 headers from GitHub
  - GetVersionFromGit.cmake: extracts version from git tags
  - Version.h.in: template for generated version header
- Update tests/CMakeLists.txt to integrate with root CMake project
  (uses FetchContent for Google Test instead of find_package)

- Remove 14 obsolete build configurations (keep MsVc2022.win):
  Bcc55.win, CC.solaris, Gcc.darwin, Gcc.freeBSD, Gcc.lin, Gcc.solaris,
  MinGW_Dev-Cpp.win, MsSDK64.win, MsVc60.win, MsVc70.win, MsVc80.win,
  MsVc90.win, VAC.aix, aCC.HP
- Remove shared makefile includes (makefile.environ, makefile.sources)
- Remove root and IscDbc makefile.in (autotools era)

- Remove vendored Firebird headers (FBClient.Headers/)
  — now fetched at build time via CMake FetchContent
- Remove vendored ODBC SDK headers (Headers/SQL.H, Headers/SQLEXT.H)
  — use system SDK instead
- Move Headers/OdbcUserEvents.h to project root
- Update OdbcConnection.h include path accordingly

- Remove non-functional old test projects: JdbcTest/, Test/, TestInstall/
- Remove tracked build artifacts (.exp files) and MinGW .def files
- Rename OdbcJdbc.dll.manifest to FirebirdODBC.dll.manifest
  (matches the reference in OdbcJdbc.rc)

- Update MsVc2022.win/OdbcFb.vcxproj:
  - Include path: FBClient.Headers -> build/_deps/firebird_headers-src/src/include
  - Header reference: Headers/OdbcUserEvents.h -> OdbcUserEvents.h
  (Requires running 'cmake -B build' first to fetch Firebird headers)

- Update .gitignore with CMake build artifact patterns

Build validation:
  CMake:  cmake -B build -G 'Visual Studio 17 2022' -A x64
          cmake --build build --config Release
          -> FirebirdODBC.dll (120 exports, matching VS 2022 build)
  VS 2022: MSBuild Builds/MsVc2022.win/OdbcFb.sln /p:Configuration=Release /p:Platform=x64
          -> FirebirdODBC.dll (120 exports)
  Tests:  375 tests, 375 skipped (no database), 0 failures

Author: fdcastel

.gitignore

@@ -11,3 +11,32 @@ Install/Win32/install_image/
 build_*.log
 OdbcJdbcSetup_*.iss
 .vs/*
+
+# CMake
+build/
+build-*/
+Build/
+out/
+cmake-build-*/
+CMakeCache.txt
+CMakeFiles/
+cmake_install.cmake
+CTestTestfile.cmake
+_deps/
+install_manifest.txt
+Testing/
+tests/Testing/
+
+# Build artifacts
+*.o
+*.obj
+*.dll
+*.lib
+*.exe
+*.pdb
+*.ilk
+*.exp
+
+# IDE
+.idea/
+.vscode/